The present invention relates to an architecture for computer expansion boards. More particularly, it relates to an architecture which reduces the number of pins required to transfer configuration bits within such board.
Many computer systems, such as the personal computer (PC) may be purchased with differing levels of functionality and/or storage capacity. Increased functionality and/or storage capacity may be obtained through upgrading a basic unit by connecting add-on boards to xe2x80x9cexpansion slotsxe2x80x9d provided on the PC. A typical expansion board is available to increase the memory capacity of the PC. Other expansion boards provide additional or supplemental processing power and/or provide interface capabilities for a variety of input/output (I/O) functions. Many such expansion boards include a microprocessor or controller to perform a designated function.
When an expansion board is added to a PC, the board may need to be provided with certain information that defines its relationship to the host or to other parts of the system. For example, a memory board that is to be addressable by the host must be provided with its starting and ending address so that it can function appropriately with respect to the other memory in the system. Other expansion boards may also have addressable memory space which requires a starting and ending address. In addition, there may be other information required by such other boards. For example, an expansion board for connecting the host to a local area network (LAN) may need information specifying its network node number, defining its interrupt level, etc.
The bits of data which define the information provided to the board are referred to as configuration bits and the act of providing the data bits to the board is referred to as configuring the board. Some boards are configured by manually operated switches which are connected to the board. These switches can be set prior to attaching the board to the host computer. When the board is powered up, the switches are read by the on board microprocessor or controller and the configuration information stored in the appropriate register for use as needed.
In the past, the on board microprocessor or controller received the configuration bits on dedicated lines. Since the microprocessor or controller is typically implemented as an integrated circuit chip, each line requires an additional pin. The number of pins used solely for configuration bits will vary but in some LAN cards is thirty-two. Together with the various control, data and address lines, the total number of pins can exceed one hundred. In general, the cost of a chip increases with an increase in the number of pins. In addition, the cost of the board to which the chip is attached is also more expensive in order to accommodate the extra pins.
It is therefore an object of the present invention to provide a new and improved circuit board for connecting to a host computer.
It is another object of the present invention to provide an enhancement board having a controller chip with a reduced number of pins.
It is a further object of the present invention to provide a new and improved method for configuring a circuit board connectable to a host computer.
It is yet another object of the present invention to provide an improved architecture for configuring an enhancement board.
One form of the present invention is a circuit board for connecting to a host computer. The board comprises a controller chip, a parallel bus, a memory for storing a plurality of configuration data bits, and a control line. The controller chip controls the operation of the board and has an internal register for storing a plurality of data bits. The parallel bus transfers data bits between the controller chip and other components on the board and is connected to the memory. The control line is connected between the controller and the memory for enabling the output of the memory to transfer the configuration bits to the internal register over the bus.
Another form of the present invention is a method for configuring a circuit board connectable to a host computer. The circuit board has a controller chip, an internal parallel data bus connected to the chip, and a memory connected to the bus. The method comprises programming the configuration data bits into the memory, providing a control signal to the memory, and transferring the configuration data bits to the controller over the bus.